Antioxidant for rubber



. iurane,

Patented Nov. 14, 1 944 a Carlin F. Gibbs, Cuyahoga Falls, out, assignor to TheB. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing. Application'August 4, 1943,

11 Claim.

This invention relates to the preservation of organic materials which tend to deteriorate by absorption of oxygen from the atmosphere and to the means for preventing such deterioration. This application is a continuation-in-part of my copending application Serial No. 405,790 filed August 7, 1941.

The preservation of such materials may be accomplished by incorporating in the material to be preserved, as an antioxidant, a hydroxyaryl derivative of 2-methy1 2-a1ky1 dihydrobenzoiurane. Among the materials which may be thus preserved are iatty oils such as linseed or tung oil, petroleum oils such as gasoline, fish oils, aldehydes, soaps, turpentine, rubbers and the like. Among the rubbers, vulcanized or unvulcanized, which may be preserved with my new compounds are all the natural rubbers such as caoutchouc, balata, gutta percha, latex, as well as artificial rubber isomers; and such synthetic rubbers as neoprene and the copolymers of butadiene-1,3

' hydrocarbons with acrylo'nitrile, styrene, methyl acrylate, methyl methacrylate, isobutylene, or the like. The term a rubber" as used in the claims is intended to designate all of the abovementioned materials. 1

The hydroxyaryl dihydrobenzofuranes which act as antioxidants are of the general formula in which R is hydrogen or an alkyl group, and

n is an integer less than three. Among these compounds are 2-methyl-4-hydroxy dihydrobenzofurane, 2-ethyl-4-hydroxy dihydrobenzo- Iurane, 2,2-dimethyl-4-hydroxy dihydrobenzofurane, 2,2-dimethyl-5-hydroxy dihydrobenzoiurane, 2,2-dimethy1-6-hydroxy dihydrobenzofurane, 2,2-dimethyl-7-hydroxy dihydrobenzo- 2-methyl-2-ethyl-5-hydroxy dihydrobenzoiurane, 2-methyl-2-propy1-4-hydroxy dihydrobenzofurane, 2-methyl-2-amy1-6-hydroxy dihydrobenzofurane, '2,2-dimethyl-4,6-dihydroxy dihydrobenzofurane, '2,2-dimethy1-4,7-dihydroxy dihydrobenzofurane, 2,2-dimethyl-5,'7-dihydroxy dihydrobenzofurane, 2-methy1 2--propyl-4,5-dihydroxy dihydrobenzofurane, 2,2-dimethyl-6,7- dihydroxy dihydrobenzofurane and the like.

As a specific example of my invention; will describe the preparation of 2,2-dimethyl-5-hydroxy dihydrobenzofurane as wellas its use as an'antioxidant in rubber. The most convenient starting on. sec-s00) materials for the synthesis of-this compound are hydroquinone and beta-methallyl chloride.

These materials, in the ratiooi' two molecular proportions of hydroquinone to one molecular 5 proportion of beta-methallyl chloride, are refiuxed with about 1.5 molecularproportions of 10% alcoholic potash for about two hours. After cooling the mixture any diether may be filtered on. After acidification the mono ether may be filtered off, washed, and dried. Other beta-alkyl allyl ethers may be prepared by similar reaction.

3000B CHFECHQCI HOGOGHSCT-CHI BC! I I 43H: The mono ether may readily be rearranged to the o-beta-methallyl derivative by heating with about one-half its weight of diethylaniline as solvent for about ten minutes at 225 to 250 C. Other solvents, such as dimethylaniline or various hydrocarbons may. also be employed. The 5 product, which boils at 130 to 140 C. at 3 mm. pressure and which melts at 82 to 84 0., may readily be separated from the reaction mixture by fractional distillation at reduced pressure.

HO OH CH: Ring closure of the alkenyl derivative is readily accomplished by heating it with pyridine chloride in the-ratio of one molecular proportion of isobutenyl hydroquinone to twomolecular proportions of pyridine hydrochloride. Usually a heating period of ten to twenty minutes at 200 to 225 C. sufiices. The product, 2,2-dimethyl-5- hydroxy dihydrobenzofurane, may be separated from the reaction mixture by washing with water and sodium bisulfite solution, drying, and distilling at reduced pressure. The-product boils at 100 to 118 C. at 3 mm. pressure and melts at hydro- 2 asoauo Other compounds of similar structure may be prepared by starting with the appropriate polyhydroxy benzene and beta-ml substituted allyl halide. The beta-alkyl group keeps its same position in the hydrocarbon chain after the rearrangement oi the ether and the cyclization reaction. The position of hydroxy groups in the benzene ring has little efiect upon the course or the reaction; however. the hydroxy group which is etherified in the first step of the reaction must have at least one ortho position open in order for the desired rearrangement to take place. Instead of using a polyhydroxy benzene as the starting material, an alkoxy dihydroxy benzene may be employed. Such compounds as hydrowiththe antioxidantsby any of theusual ods. The antioxidant may be-used as a intheform ofasolution: itmaybemixedwith the rubber latex before or it may beaddedtothesolidrubberonarollmill in an internal mixer, or itmay be applied to the surface or the finished rubber article. In general, from 0.1 to 5.0 percent or mm'eot my new quinone, catechol, resorcinol. hydroxy hydroquinone, pyrogallol, phloroglucinol, and the like are useful starting materials. Among the beta-aikyl allyl halides which may be used are beta-methallyl, beta-ethylallyl, beta-propylallyl, beta-butylailyi, beta-hexylallyl. etc.. chloride or bromide.

As an example or the antioxidant efi'ect of these compounds the following rubber compositions were prepared, in which the parts are by weight:

The two compositions were vulcanized in a press at 280 F. and were then tested in a Di Mattia flexing machine at room temperature. The samples were inspected after the indicated number of flexures and were given a rating between (no cracks) and (complete rupture). The results are as follows:

As is clear from the table, the rubber composition containing 5-hydroxy-2,2-dimethyl dihydrobenzofurane withstood more than twice as many compounds are efl'ective to the deterioration of the materials in which they are incorporated. 7

Although I have herein disclosed specific embodiments or my invention, I do not intend to limit myself solely thereto, but only to the extent indicated in the appended claims.

I claim:

1. The method of retarding the deterioration of an organic compound which tends to deteriorate by absorption or oxygen from the air which comprises treating it with a compound having the structure OH: (110) L/ compound having the structure I cm no) e n inwhichRisamemberoftheclass w a: of

hydrogen andalkyl groups and n is an integer flexures before rupture as did the rubber composition containing no antioxidant. Similar results may be obtained with other similar compounds.

less than three.

3. The method 0! retarding the deterioration oi. rubber which comprises treating it with a W 5 compoimdhavingthestructm'e 0 or CO EJTL n. in whichRisamemberoitheclass or hydrogen and alkyl groups and u is an integer less than three.

4. The method or retarding the deterioration of a rubber which comprises treating it with a compound havingthestructure in'whichnisanintegerlessthanthree. 5. The method orretarding the deterioration Any f the u l p m y relnor a rubber which comprises treating it with a compound havingthestructure 6. The method retarding the deterioration of a rubber which comprises treating it with 2,2; 3

The rubber-or other material may betreated M y 8 7 Y l'm 7. A composition comprising a rubber and a compound having the structure in which R is a member of the class consisting of hydrogen and alkyl groups and n is an integer less than three.

8. A composition comprising rubber and a compound having the structure in which R is a member of the class consisting of 'hydrogen and alkyl groups and n is an integer less than three.

9. A composition comprising a rubber and a compound having the structure E To no 5 I)I c in which n is aninteger less than three.

10. A composition comprising a rubber and a compound having the structure 1 dimethyI-S-hydroxy dihydrobenzofurane.

. CARLIN F. GIBBS. 

